The Gateway Program was established by the Province of British Columbia,
as a means of addressing growing traffic congestion throughout Metro Vancouver.
The Port Mann/Highway 1 (PMH1) Improvement Project is a component of the
Gateway Program, the largest infrastructure transportation project in the
history of British Columbia. In February 2009 the Province announced it
would enter into a contract with the preferred component to design and
build the new, 10-lane Port Mann Bridge and Highway 1 improvements.

This massive $2.4 billion infrastructure project was a five year design
build contract with its primary objective of reducing travel time by up
to 30%. In addition to the new Port Mann Bridge, the project required the
widening of 37 kilometres of freeway from Vancouver to Langley which also
included widening of seven Highway 1 overpasses, replacing nine Highway
1 interchanges, built or rebuilt of 15 new overpasses and underpasses at
the Cape Horn interchange.

Reinforced Earth Company (RECo) was awarded the contract to design and
supply the Mechanically Stabilized Earth wall for the project. Overall,
RECo provided approximately 70 MSE walls that total over 37,000m2
of wall face area. RECo’s walls types included Abutment Walls and 2-stage
retaining walls in heights up to 12m. RECo was involved in all three segments
of the PMH1 project.

The East Segment is located east of the Port Mann Bridge; two additional
lanes in each direction were built to 200 Street. A total of 17 walls were
designed and supplied in this segment by RECo that included seven (7) bridges
with a total of fifteen (15) perched abutment walls:

In addition to the bridge abutment walls, RECo designed and supplied eleven
(11) other retaining walls with TerraClass system including off-ramps at
the 156th Street intersection.

The Central Segment included the Cape Horn interchange which required extensive
upgrade where RECo designed and supplied sixteen (16) MSE structures. Due
to poor ground condition, the majority of construction was carried out
on an improved ground. To help accommodate settlements, RECo designed ten
(10) 2-stage walls, with about 7,000m2 facing area; as well
as four (4) walls undertaking EPS blocks surcharge. The 2-stage wall consists
of TerraTrel facing in the first stage and TerraClass facade in the second
stage. The TerraTrel wall is a wire-mesh facing wall that can flex and
can tolerate larger settlements as compared to the TerraClass system. The
first stage is the TerraTrel wall which is also considered as a preloading.
After the preloading stage is complete, the facade panels are installed
and connected to TerraTrel facing utilizing connector rods and coil loops.
The void between the two facings is filled with self-compacting gravel.

The West Segment is located west of the Central Segment. One additional
general purpose lane was added in each direction resulting in widening
and replacing of overpasses and interchanges. Reinforced Earth walls were
used in widening and replacing of the following structures in the West
Segment:

One of the challenges in the PMH1 project was the performance based seismic
design that was mandated by the Ministry of Transportation of British Columbia.
The required seismic performance criteria for MSE walls were dependent
on the return period of the design earthquake. The three performance
criterial were 1) immediate functionality, 2) repairable damage and 3)
no collapse after project design earthquakes with return periods of 475,
975 and 2475 years, respectively. A specialized geotechnical consultant
was retained to carry out rigorous analyses based on response spectra and
multiple time-histories. Naesgaard Geotechnical Ltd. performed a series
of two dimensional numerical dynamic analyses using the program FLAC to
assess the internal stability of Reinforced Earth walls in 5 defined cases.
The internal design of the wall sections for these cases were designed
by RECo utilizing a pseudo-static method and then modeled in FLAC to be
analyzed for deformations under different seismic events. Numerical
analyses indicated that the relative displacements within the Reinforced
Earth structure were well below the allowable rupture strain and met the
Design Build Agreement requirements.